1. Field of the Invention
The present invention relates to a communication processing apparatus, a communication control method and a computer program. In particular, the invention relates to a communication processing apparatus, communication control method and computer program that perform proper control for preventing an adverse effect on an existing communication stream by applying Admission control in a construction in which data communication is performed by using priority-based QoS (Quality of Service).
2. Description of the Related Art
With the wide spread of data communication over a network such as the Internet and a LAN, many households apply a home network including the connection of a household electric appliance, a computer and other peripherals over a network. The home network may allow, for example, the exchange of contents between network-connected equipment, provide the convenience and comfort to users and will be spread increasingly in the future.
So-called streaming data distribution and reproduction processing in which a client side can simultaneously receive and reproduce data is allowed by, for example, defining, as a server, equipment having a receiving portion such as a tuner provided in a household and a storage unit such as a hard disk and transmitting contents such as a movie held by the server to a client apparatus such as a PC that a user has over a network.
The server that performs such streaming data distribution performs data processing such as encoding and creates and outputs send data to the network. On the other hand, the client that reproduces the streaming data temporarily stores received data in a buffer and then performs decoding processing and reproduction processing sequentially.
However, multiple pieces of communication data may conflict over the network. When the conflict among multiple pieces of communication data occurs, the communication band may be insufficient, and a problem such as delay of the distribution of the streaming data may occur. Various constructions for controlling conflicting communication data have been proposed. For example, Patent Document 1 discloses a construction allowing communication by defining a conflicting transmission domain in which communication stations conflict to transmit information and a priority transmission domain in which a band with a higher priority is defined to transmit information and choosing the conflicting transmission domain or the priority transmission domain based on the buffer-stored amount in a communication station.
QoS (Quality of Service) has been known as a communication control construction for guaranteeing the quality of data transmission. QoS may perform control in which a band is assigned to each communication data based on the priority. For example, in order to implement realtime reproduction in streaming data distribution of moving pictures, a packet included in the moving pictures may be required to transmit from a streaming server to a streaming client without delay. On the other hand, some data packets may allow delay in time. The communication packet to be transferred over a network may undergo communication control processing based on the identification of the processing priority.
A data transfer control apparatus such as a router and a switch connecting to a network, for example, may function as a communication control processing apparatus for providing QoS, that is, for guaranteeing the quality of data transfer. Various methods for defining priorities have been proposed including a method defining priorities in data flows, each of which is identified by a sender address and a receiver address, QoS based on band reservations and QoS based on priorities in which communication control is performed based on the priority added to a packet.
IEEE (The Institute of Electrical and Electronics Engineers) 802.1D (which may be called 802.1p priority), which is one of standard specifications relating to a wireless network, specifies a system of priority-based QoS for performing communication control based on the priority added to a packet in a wired LAN such as an Ethernet (registered trademark). Wi-Fi forum specifies priority-based WMM (Wi-Fi Multimedia), which is a subset of 802.11e. 802.11e is a QoS specification for a wireless LAN. These priority-based QoS technologies are easier to implement and more effective than the band-reservation-based QoS. Thus, Digital Living Network (DLN), which is an industrial standard of home network technologies, will adopt both 802.1D and WMM.
For example, the streaming data distribution of two AV contents may have a same priority defined and be performed in parallel in accordance with DLNA (Digital Living Network Alliance) guideline specified by Digital Living Network (DLN), which is an industrial standard of home network technologies. In this case, however, when the network band is not sufficient for transmitting the two lines of streaming, both of the two lines of streaming may not maintain a sufficient transfer rate for performing realtime reproduction at a client. Thus, both of the two pieces of streaming data may have turbulence in reproduced images and/or voice interruption at the client, which is a problem.
In order to solve the problem, a system of Admission Control has been proposed which manages the communication traffic on a network unitedly, examines whether realtime reproduction is available or not when a new line of streaming is started, and permits the start of data distribution only if available. However, the system is complex to implement and has not been embodied yet. Furthermore, the problem on the operation of the policy of Admission Control has not been solved yet.
Patent Document 1: JP-A-2005-198008